The overall aim of this continuing project is to investigate the neural basis of cognitive control. In the first 4 years of the project, we have conducted several dozen experiments that have focused on the neural basis of attentional control using functional magnetic resonance imaging (fMRI) and suitably designed cognitive paradigms. We now propose experiments to extend this work into the domain of task switching. The extension is a natural one in that the control of attention shifts can be viewed as a special case of task switching. We conceptualize a task as a combination of (a) one or more relevant or attended sensory inputs (e.g., digits at different locations on a computer screen), (b) the cognitive operation(s) that must be performed on the inputs (e.g., decide if the digit is even or odd), (c) the rule that maps the outcome of the cognitive operation to a specific behavioral response (e.g., 'if even, move left;if odd, move right'), and (d) the motor response set (e.g., eye movements or manual button presses). Task switching is the deliberate replacement of one or more of these task components with another. The experiments we have conducted so far have provided insights about the neural mechanisms of attention switches (i.e., switching inputs) in isolation, and have permitted us to optimize our cognitive paradigms for fMRI. The proposed experiments extend these studies to the other task components (operations, mapping rules, and response sets) and to combinations of components. The specific aims of the project are (1) to investigate the neural circuits that are involved in controlling input, operation, mapping, and response set switches alone and in combination;(2) to investigate the control of switching to and from tasks that are automatic vs. controlled;(3) to investigate the role of between-task crosstalk and cue switches vs. task switches and (4) to correlate behavioral measures of task switching with cortical signatures of task switching. The proposed project will advance our understanding of the neural basis of cognitive control during task switching, and this in turn will contribute to our understanding of impairments of cognitive control caused by brain damage or drug abuse.